1. Field of the Invention
This invention relates to a radiation image storage panel for recording and reproducing a radiation image having a fluorescent layer comprising a stimulable phosphor which stores radiation energy and emits light upon stimulation thereof, and more particularly to a radiation image storage panel the edge faces of which are reinforced.
2. Description of the Prior Art
As is well known in the art, a photographic method using a silver salt as radiography in which an X-ray film having an emulsion layer comprising a silver salt is used in combination with an intensifying screen has generally been employed to obtain a radiation image. A method which provides a radiation image of higher resolution and sharpness than the radiation image provided by the conventional photographic method is disclosed, for example, in U.S. Pat. No. 3,859,527, U.S. Pat. No. 4,236,264, Japanese Unexamined Patent Publication No. 163,472/1980 corresponding to U.S. Pat. No. 4,315,318 and Japanese Unexamined Patent Publication No. 116,340/1980 corresponding to U.S. Pat. No. 4,276,473. In the method of the patents, there is used a radiation image storage panel comprising a stimulable phosphor which emits light when stimulated by an electromagnetic wave selected from among visible light and infrared rays after exposure to a radiation. (The term "radiation" as used herein means electromagnetic wave or corpuscular radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, high-energy neutron rays, cathode rays, vacuum ultraviolet rays, ultraviolet rays, or the like.) The method comprises the steps of (i) causing the stimulable phosphor of the panel to absorb a radiation passing through an object, (ii) scanning the panel with an electromagnetic wave such as visible light or infrared rays (hereinafter referred to as "stimulating rays") to sequentially release the radiation energy stored in the panel as light emission, and (iii) electrically converting the emitted light into an image.
The radiation image storage panel employed in the above-mentioned method for recording and reproducing a radiation image comprises a substrate, a fluorescent layer provided on the substrate and a protective layer provided on the fluorescent layer. The fluorescent layer comprises a binder and a stimulable phosphor dispersed therein. When the radiation image storage panel having the above-mentioned structure is used in the method for recording and reproducing a radiation image, the edge faces of the panel, particularly the fluorescent layer portions in the edge faces of the panel, are easily damaged. Therefore, the edge faces of the radiation image storage panel need to be reinforced. That is, the radiation image storage panel needs to be edge-reinforced.
The conventional radiographic intensifying screen is edge-reinforced by coating the edge faces thereof with an abrasion resistant material. Resins such as vinyl acetate resin and vinyl chloride resin have been practically used in the edge-reinforcement of the conventional radiographic intensifying screen. Since the above-mentioned structure of the radiation image storage panel is similar to that of the radiographic intensifying screen, it is intended to edge-reinforce the radiation image storage panel with the materials which have been practically used in the edge-reinforcement of the conventional radiographic intensifying screen.
However, the materials which have been practically used in the edge-reinforcement of the conventional radiographic intensifying screen are inadequate as the edge-reinforcing material for the radiation image storage panel. This is because the radiation image storage panel is handled more roughly than the radiographic intensifying screen and the edge faces of the panel are liable to receive strong mechanical shock. That is, in contrast to the radiographic intensifying screen which is always held in a cassette during the use thereof, the radiation image storage panel must be taken out from a cassette after exposure to radiation in order to read out the radiation image recorded in the panel by exposing the panel to stimulating rays. Further, since differently from the radiographic intensifying screen, the radiation image storage panel is repeatedly used in accordance with a continuous cycle comprising steps of exposing the panel to a radiation, reading out the radiation image recorded in the panel and removing the radiation energy remaining in the panel, the panel must be moved from one step to the next step by means of a carrier. During the above-mentioned handling, the radiation image storage panel is liable to receive strong mechanical shock on the edge faces thereof. Therefore, the edge faces of the radiation image storage panel need to be reinforced to a considerably higher extent than that of the radiographic intensifying screen so that the edge faces are not damaged during the above-mentioned rough handling of the panel.